分支系统学和种系发生种

简要评述进化系统学和分支系统学的物种概念问题。介绍了关系物种问题研究的一些新进展,特别是种系发生种概念和种系发生种的划定方法－居群聚合分析和分支单型聚合。     

Studies in the morphology and systematics of berberidaceae

The floral vasculature in three allied genera,Plagiorhegma, Jeffersoria andAchyls is investigated, and the results are compared with those ofEpimedium andVancouveria which are related closely toPlagiorhegma andJeffersonia. The vasculature in the receptacle ofPlagiorhegma andJeffersonia is similar, but that ofAchlys is much simpler. Slightly different trace patterns are observed in the sepals ofPlagiorhegma andJeffersonia. InJeffersonia, the 3-trace condition leaving 2 or 3 gaps is most frequently observed, but inPlagiorhegma traces of a double nature leaving a single gap are more frequent. The traces to the innermost sepals, petals and stamens are usually of a double nature leaving a single gap in both genera. Regular division and fusion are not observed in the receptacular stele. The vascular differentiation between sepals and petals is more advanced inPlagiorhegma andJeffersonia than inEpimedium andVancouveria. InAchlys, the traces are all staminal and single throughout their course. Two parts recognized in the pistils ofPlagiorhegma, Jeffersonia andAchlys are traversed by independent vasculature. The comparisons of pistil morphology including vasculature ofPlagiorhegma, Jeffersonia, Achlys, Epimedium andVancouveria lead to the interpretation that the pistils are based on the same morphological plan. The probable evolutionary trend in pistil is then suggested in these five genera.     

Claims and limits of phylogenetic systematics1

Within the methodology of phylogenetic systematics four hierarchic levels are distinguished: the “Central Claim” (to reconstruct phylogeny), methodoloical postulate (to conclude analysis with a purely dichotomous cladogram if ever possible), method (search for sister-group relationships by character analysis), and “Taxonomic Principle” (establishment of a classification reflecting merely the recognized genealoy). Certain limits of applicability and reliability of traditional phylogenetic systematics are specified: genealogy can only be analysed among taxa with perceptible evolutionary novelties; reticulated genealogy is not yet regarded; events other than cladogenetic ones cannot be recognised. Phylogenetic systematics is an independent method which has not been absorbed by any type of “pattern” or “transformed” cladism. Phylogenetic systematics relies on the theory of evolution, which does not lead into circularity, since phylogenetic systematics does not claim to prove or to explain evolution whatsoever.     

Turbellaria Lecithoepitheliata: morphology,systematics, phylogeny

A review of the literature on the world fauna of lecithoepitheliata and Prolecithophora and extensive observations by the author on species of the Prorhynchidae, including cosmopolitan species as well as some endemic to Lake Baikal, and on endemic species of Baicalarctiinae (Prolecithophora) show that the Prorhynchidae and Gnosonesimidae are properly classified in the Neoophora. The morphological similarity of the Prorhynchidae and Prolecithophora proves these taxa are closely related. A hypothesis relating the Lecithoepitheliata Prorhynchidae to primitive prolecithophorans appears to be the only tenable hypothesis on the phylogeny of Lecithoepitheliata. The question of whether the Lecithoepitheliata is monophyletic still needs investigation; more evidence on the phylogeny of the Gnosonesimidae is needed.     

Computationally difficult parsimony problems in phylogenetic systematics

A basic problem in phylogenetic systematics is to construct an evolutionary hypothesis, or phylogenetic tree, from available data for a set of operational taxonomic units (OTUs). Associated with the edges of such trees are weights that usually are interpreted as lengths. Methods proposed for constructing phylogenetic trees attempt to select from among the myriad alternatives a tree that optimizes in some sense the fit of tree topology and edge lengths with the original data. One optimization criterion seeks a most parsimonious tree in which the sum of edge lengths is a minimum. Researchers have failed to develop efficient algorithms to compute optimal solutions for important variations of the parsimonious tree construction problem. Recently Graham & Foulds (1982) proved that a special case of the problem is NP-complete, thus making it unlikely that the computational problem for this case can be solved efficiently. I describe three other parsimonious tree construction problems and prove that they, too, are NP-complete.     

Pollen morphology and systematics of Burseraceae

The Burseraceae are a medium‐sized family in which 18 genera are currently recognised. They are the subject of a long‐term project to describe the pollen morphology from light, scanning electron and transmission electron microscopy. The pollen morphology of tribe Protieae has been published, as well as an account of the pollen of the African taxa in the family. Pollen data for the other two tribes, Bursereae and Canarieae, are more or less complete. The pollen of all the genera have been examined, with the exception of the recently described Pseudodacryodes Pierlot for which, currently, there is no pollen material available. This paper summarises the results.

There is considerable variation in exine and aperture features between, and occasionally within, the genera and 14 major pollen types are defined, including two previously undescribed types: ‘Canarium oleiferum’ and ‘Canarium gracile’. The distribution of pollen characteristics throughout the family is compared with previously published tribal and subtribal groupings, as well as with current ideas of generic relationships from molecular analyses. Comparisons show notable congruence of pollen data with molecular data. To some extent pollen morphology is different for each of the subtribes. Nevertheless, there are some notable exceptions, for example, the pollen of Garuga and Boswellia are remarkably similar, although Garuga has been included, somewhat tenuously, in tribe Protieae, and Boswellia is included in tribe Bursereae, subtribe Boswelliinae. In a recent molecular tree Garuga and Boswellia appear to be closely related, and this supports the conclusion, based on several macromorphological characters as well as pollen, that Garuga should be transferred to tribe Bursereae.     

Ecology,morphology, and systematics of jepsonia (Saxifragaceae)

Aspects of flowering, leaf production, caudex and contractile root morphology, edaphic preferences, and systematics ofJepsonia (Saxifragaceae) are discussed. Although other authors have recognized as few as one species ofJepsonia, various lines of evidence suggest that three allopatric species can be recognized, which are morphologically distinct and separated from each other by barriers to hybridization. These species areJ. heterandra of the Sierra Nevada foothills of California,J. malvifolia of southern California’s offshore islands and the Mexican Guadalupe Island, andJ. parryi of mainland southern California and adjacent Baja California. Plants flower from late summer to early winter in response to environmental factors that have yet to be clearly identified. Flowers are heterostylous, and the species are self-incompatible. Pollination is by syrphid flies and halictid bees. Leaves are produced during or after flowering in response to rain. They persist through the winter until the onset of the dry season in the subsequent late spring. Plants perennate by a starchy underground structure, which is hypocotylar in origin and best termed a caudex. Young plants and many old ones also produce one or more very large, whitish, starch-free contractile roots that are annual in duration.Jepsonia heterandra characteristically is restricted to the crevices of slatelike rocks, although the other two species occur in a wider range of edaphic situations. Moisture and temperature conditions, as well as rodent predations, may determine the general and local distribution of the species. The relationships of the genus are briefly considered, and interspecific differences are described.     

The role of parsimony,outgroup analysis,and theory of evolution in phylogenetic systematics

It is argued that both the principle of parsimony and the theory of evolution, especially that of natural selection, are essential analytical tools in phylogenetic systematics, whereas the widely used outgroup analysis is completely useless and may even be misleading. In any systematic analysis, two types of patterns of characters and character states must be discriminated which are referred to as completely and incompletely resolved. In the former, all known species are presented in which the characters and their states studied occur, whereas in the latter this is not the case. Dependent on its structure, a pattern of characters and their states may be explained by either a unique or by various conflicting, equally most parsimonious hypotheses of relationships. The so-called permutation method is introduced which facilitates finding the conflicting, equally most parsimonious hypotheses of relationships. The utility of the principle of parsimony is limited by the uncertainty as to whether its application in systematics must refer to the minimum number of steps needed to explain a pattern of characterts and their states most parsimoniously or to the minimum number of evolutionary events assumed to have caused these steps. Although these numbers may differ, the former is usually preferred for simplicity. The types of outgroup analysis are shown to exist which are termed parsimony analysis based on test samples and cladistic type of outgroup analysis. Essentially, the former is used for analysing incompletely resolved patterns of characters and their states, the latter for analysing completely resolved ones. Both types are shown to be completely useless for rejecting even one of various conflicting, equally most parsimonious hypotheses of relationships. According to contemporary knowledge, this task can be accomplished only by employing the theory of evolution (including the theory of natural selection). But even then, many phylogenetic-systematic problems will remain unsolved. In such cases, arbitrary algorithms like those offered by phenetics can at best offer pseudosolutions to open problems. Despite its limitations, phylogenetic systematics is superior to any kind of aphylogenetic systematics (transformed cladistics included) in approaching a (not: the) “general reference system” of organisms.     

The threefold parallelism of Agassiz and Haeckel,and polarity determination in phylogenetic systematics

A parallel exists between the threefold parallelism of Agassiz and Haeckel and the three valid methods of polarity determination in phylogenetic systematics. The structural gradation among taxa within a linear hierarchy, ontogenetic recapitulation, and geological succession of the threefold parallelism resemble outgroup comparison, the ontogenetic method, and the paleontological method, respectively, which are methods of polarity determination in phylogenetic systematics. The parallel involves expected congruence among similar components of the distribution of character states among organisms. The threefold parallelism is a manifestation of a world view based on linear hierarchies, whereas polarity determination is part of the methodology of phylogenetic systematics which assumes that organisms are grouped into a nested hierarchy. The threefold parallelism facilitated the ranking of previously established taxa into linear hierarchies consisting mostly of paraphyletic groups. In contrast, methods of polarity determination identify apomorphies that determine and diagnose monophyletic taxa (clades) in the nested genealogical hierarchy. Taxa in linear hierarchies are defined by sets of character states, whereas clades are defined by common ancestry. Although the threefold parallelism was ostensibly abandoned with the rejection of Haeckel's biogenetic law, some of its components continue to facilitate the progressive scenarios that are common in evolutionary thought. Although a general view of progression in organismal history may be invalid, the progressive or directional sequence of character state changes that results in the characterization of a particular clade has considerable heuristic value. Agassiz's ostensibly nested hierarchy and other pre-Darwinian classifications do not provide support for the view that the natural system can be discovered without recourse to the principle of common descent.     

Anthocyanins of the Sterculiaceae: Flavonoid scores and Hennigian phylogenetic systematics

Published results of the distribution of anthocyanins in the Sterculiaceae have been re-interpreted on the basis of the phylogenetic status of the compounds present. A flavonoid score system was less useful than a cladistic interpretation based on Hennigian arguments.     

Descriptions and phylogenetic systematics of Myxobolus spp. from cyprinids in Algonquin Park, Ontario

Eight species of Myxobolus were collected from four species of cyprinids in Algonquin Park, Ontario. On the basis of spore morphology, five of these species are described as new and two are redescribed. The evolutionary relationships among these eight species were studied using partial small subunit ribosomal DNA (ssu-rDNA) sequence data. The resulting cladograms, which were highly resolved and with strongly supported relationships, allowed for the evaluation of spore morphology, host specificity, and tissue tropism, criteria traditionally used in species identification. These criteria, recently criticized for creating artificial rather than natural taxonomic groupings, were evaluated for their reliability in the systematics of the species examined. The data showed that distantly related species often infect the same host and tissue, and that closely related species often occur in different hosts. Morphologically similar species are more closely related to each other and the taxonomy based on spore morphology is consistent with the relationships depicted in the phylogenies. These results suggest that spore morphology is better than host specificity and tissue tropism as a species character, as well as for determining evolutionary relationships among the species of Myxobolus examined.     

Comparative detailed morphology of the Heteroderinae Filip'ev & Schuurmans Stekhoven, 1941, sensu Luc et al. (1988): phylogenetic systematics and revised classification

Taxonomic schemes for the Heteroderinae Filip'ev & Schuurmans Stekhoven, 1941, sensu Luc et al., (1988) have been unstable due to the large number of genera and the paucity of known reliable characters. Reliable characters are essential when using phylogenetic inference in developing a natural classification. Morphological and developmental studies using light, scanning and transmission electron microscopy have revealed the new characters of host response, en face patterns, phasmid structure and female cuticular layers. These techniques also gave us insight into the homoplasy and polarity of many characters, revealed previously undetected character states and clarified misinterpreted character states. A matrix with the 19 most reliable characters is proposed for 20 operational taxonomic units (OTUs) and we employ this matrix for comparing computer generated phylogenetic analyses of the PHYLIP and PAUP packages. PAUP was deemed the more reliable parsimony algorithm for phylogenetic analysis of the Heteroderinae (Fink, 1986; Platnick, 1987). Monophyly of Atalodera + Sherodera + Thecavermiculatus (tribe Ataloderini), and Cactodera + Heterodera + Afenestrata, as well as Punctodera + Globodera + Dolichodera is supported by both programs. Most importantly, analyses strongly support monophyly of all cyst-forming genera (tribe Heteroderini) contrary to previous hypotheses of repeated evolution of the cyst (Wouts, 1985). In addition, monophyly of the Heteroderini with the Ataloderini is demonstrated. PAUP indicates monophyly of Sarisodera + Rhizonema + Bellodera + Hylonema and Ekphymatodera (tribe Sarisoderini new rank). Monophyly of the Sarisoderini was at first only weakly supported, but, subsequently, the reduced width of the submedial lips of second stage juveniles and males was recognized as a synapomorphy which strengthened subsequent PAUP trees and monophyly of the tribe. The present study rejects as paraphyletic or polyphyletic several previously proposed combinations, including Thecavermiculatus sequoiae (versus Rhizonema sequoiae), Sarisodera africana (versus Afenestrata africana), Dolichodera andinus (versus Thecavermiculatus andinus). The question whether T. andinus is a distinct genus, was not resolved due to insufficient data. PAUP supports our previous observations that Cactodera betulae is intermediate in a transformation series between other Cactodera and Heterodera: it also indicates these species as bring monophyletic with Heterodera + Afenestrata, but not with other Cactodera. Although these phylogenetic analyses strongly support some relationships, they indicate unresolved alternative hypotheses for others. Meloidodera (tribe Meloidoderini) and Cryphodera (tribe Cryphoderini) must be investigated for consideration of a possible synapomorphy not included in the present data matrix. Future studies are proposed to more clearly define the monophyly of the Heteroderini, as well as the Sarisoderini. Tests are also proposed to clarify questions of the monophyly of Verutus (tribe Verutini new rank) with the Heteroderinae versus other Tylenchida.     

A molecular phylogenetic approach to the systematics of Cylindropuntieae (Opuntioideae,Cactaceae)

Previous taxonomic schemes for the Cylindropuntieae were re‐evaluated in the light of a molecular phylogeny derived from a Bayesian, maximum‐likelihood and parsimony reconstructions with three plastid regions (atpB‐rbcL, psbA‐trnH and trnK/matK data sets). The reconstruction revealed that Corynopuntia and Grusonia as currently defined were polyphyletic. Quiabentia, Micropuntia, Pereskiopsis and Cylindropuntia were the only genera recovered as monophyletic. Grusonia s.s. (only including G. bradtiana) is nested in a polytomy with the rest of the species of Corynopuntia. Grusonia s.l. (G. bradtiana plus Corynopuntia) and Corynopuntia as currently defined are polyphyletic because G. pulchella is sister to Pereskiopsis. Some previous taxonomic proposals for Cylindropuntia and Grusonia recognized polyphyletic series and subgenera that do not conform to the strongly supported monophyletic groups here recovered. This study proposes redefining the polyphyletic Grusonia excluding G. pulchella in order to recognize a strongly supported monophyletic genus and the acceptance of a monotypic Micropuntia (G. pulchella) avoiding a new combination into Pereskiopsis. The infrageneric classification for Grusonia is discussed and the recognition of only four monophyletic strongly supported series (Bigelovianae, Imbricatae, Leptocaules and Ramosissimae) for Cylindropuntia is presented.